HR: 1340h
AN: GP33A-0103    [Abstracts]
TI: Do Geomagnetic Variations Affect the Foliar Spiral Direction of Coconut Palms?
AU: * Minorsky, P V
EM: pminorsky@mercy.edu
AF: Mercy College, Division of Natural Sciences 555 Broadway, Dobbs Ferry, NY 10522 United States
AU: Bronstein, N B
EM: nbronstein@ mercy.edu
AF: Mercy College, Division of Natural Sciences 555 Broadway, Dobbs Ferry, NY 10522 United States
AB: In coconut palms, leaves are attached to the stem in either an ascending clockwise (left-handed or L) or counter-clockwise (right-handed or R) spiral (1). Foliar spiral direction (FSD) is a classic case of morphological antisymmetry, in which dextral and sinistral forms are not inherited and are equally common within a species (2). FSD would seem a simple stochastic process unworthy of further study if not for the observation, based on data collected from 71,640 coconut palms in 42 locations around the world, that the FSD of coconut palms varies with latitude: R-trees predominate in the N Hemisphere and L-trees predominate in the S Hemisphere (3). Hemispheric asymmetries in FSD are significantly better correlated with magnetic latitude than with geographic or geomagnetic latitude, suggesting that latitudinal asymmetries in FSD might be associated with the temporally varying component of Earth's magnetic field (4). Here, we present two new lines of evidence that geomagnetic variations may underlie asymmetries in palm FSD. First, we show that asymmetries occur in the FSD of palm populations on opposite sides of islands, and second, that asymmetries in FSD vary with the 11-year solar cycle. The prediction that asymmetries in coconut palm FSD should exist on opposite sides of islands arises from the fact that because seawater is more electrically conductive than land, induced earth currents divide and stream past an island more strongly in one particular direction. The "geomagnetic island effect" is characterized by a complete reversal of the vertical Z component of short-period geomagnetic field anomalies at observation points on opposite sides of islands (5). To examine whether FSD varied around the circumferences of islands, we collected data on 6 islands (Puerto Rico, n = 4311; Antigua, n = 2038; Hawaii, n = 3552; Maui, n = 2175; Tahiti, n = 1582; Moorea, n = 2116). For each population, the degree of asymmetry was determined by calculating an "asymmetry quotient" (AQ) based on the formula: AQ = (L - R)/Total Asymmetries in FSD were evident on opposite sides of all the islands studied. It is of interest to consider whether the "palm island effect" described here bears any relation to the "geomagnetic island effect." The most detailed map of the "geomagnetic island effect" for a tropical island exists for Tahiti (5). In this map, P_x is a scaled parameter representing the Z component of the anomalous geomagnetic field that arises from the distortion of electric current flowing in the ocean around Tahiti. We found a close correlation (r = 0.94) between P_x and the AQs of coconut palm populations on Tahiti. Using data provided in (1), we also examined whether asymmetry in FSD varies with the solar cycle. Of 384 trees, 331 fell into one of 7 cohorts of 25 trees or more. A strong correlation (r = 0.91) was found between the AQs of the 7 cohorts and the total average monthly sunspot numbers during the 2 years following planting. This suggests that the strength of the symmetry-breaking signal, like the frequency of Pc1 geomagnetic pulsations (6), is 1 to 2 years out of antiphase with the solar cycle. We propose that Pc1-induced earth currents, which are measurable in trees (7), may bias the diffusion of morphogens in coconut palm embryos, thereby giving rise to asymmetries in FSD. 1. Davis, T.A. J. Genet. 58, 42-50 (1962) 2. Palmer A.P. Science 306, 828-833 (2004) 3. Davis, T.A., Davis, B. Math. Modell. 8, 730-733 (1987) 4. Minorsky P.V. Ann. Bot. 82, 133-140 (1998) 5. Yamaguchi S. et al.. J Geomagn. Geoelectr, 44, 43-54 (1992) 6. Fraser-Smith A.C. J Geophys Res 75, 4735-4745 (1970) 7. Fraser-Smith A.C. Nature 271, 641-642 (1978)
DE: 0402 Agricultural systems
DE: 0614 Biological effects
DE: 7904 Geomagnetically induced currents
DE: 7974 Solar effects
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005